Patterns of brain computed tomography infarction and carotid plaque echogenicity

Ultrasound Assessment of Extracranial Carotids and Vertebral Arteries in Acute Cerebral Ischemia

Assessing ischemic etiology and mechanism during the acute phase of an ischemic stroke is crucial in order to tailor and monitor appropriate treatment and determine prognosis. Cervical Duplex Ultrasound (CDU) has evolved since many years as an excellent screening tool for the evaluation of extracranial vasculature. CDU has the advantages of a low cost, easily applicable, bed side examination with high temporal and spatial resolution and without exposing the patients to any significant complications. It represents an easily repeatable test that can be performed in the emergency room as a first-line examination of cervical artery pathology. CDU provides well validated estimates of the type of the atherosclerotic plaque, the degree of stenosis, as well as structural and hemodynamic information directly about extracranial vessels (e.g., subclavian steal syndrome) and indirectly about intracranial circulation. CDU may also aid the diagnosis of non-atherosclerotic lesions of vessel walls including dissections, arteritis, carotid-jugular fistulas and fibromuscular dysplasias. The present narrative review outlines all potential applications of CDU in acute stroke management and also highlights its potential therapeutic implications.

Predictors and Consequences of Silent Brain Infarction in Patients with Asymptomatic Carotid Stenosis

AIM

Silent brain infarction (SBI) is associated with an increased risk of stroke in patients with asymptomatic carotid stenosis (ACS), and is therefore one of the criteria for performing carotid endarterectomy (CEA). Despite an extensive literature, this issue is still a matter of debate. Aim of the present work was to evaluate incidence and predictors of SBI in patients undergoing CEA for ACS, and to investigate its possible impact on CEA outcome.

METHODS

All patients submitted to CEA in a single academic center from 2005 to 2019 were prospectively inserted into a specific database. The presence of SBI was evaluated by preoperative computed tomography (CT), considering exclusively infarctions in the carotid territories from an athero-embolic source. Preoperative characteristics were investigated as possible risk factor for SBI at the uni- and multivariate analysis. The impact of SBI on stroke occurrence after CEA was also evaluated.

RESULTS

In the designated period, over a total of 1288 ACS considered and submitted to CEA, 105 (8.2%) were associated with SBI. Male sex, hypertension, dyslipidaemia, smoking, contralateral carotid occlusion and severity of carotid stenosis were associated with SBI at the univariate analysis; preoperative statin therapy showed to be a protective factor. At the multivariate analysis, contralateral carotid occlusion and severity of stenosis were independently associated with SBI (OR: 3.16, 95%CI 1.62-6.18, P=.001; OR: 1.04, 95%CI 1.01-1.07, P=.004, respectively), with statin therapy confirmed as a protective factor (OR: 0.60, 95%CI: 0.40-0.92, P=.002). Overall post-CEA stroke rate was 0.9%, with a higher post-operative risk independently predicted by the presence of SBI (OR:4.23, 95%CI: 1.40-12.73, P=.01).

CONCLUSION

SBI is present in 8% of patients with ACS, and is significantly associated with contralateral carotid occlusion and severity of the carotid stenosis. Statin therapy reduces the occurrence of this phenomenon. The presence of SBI should be carefully considered in indication to CEA since it significantly increases the surgical risk.

Hemispheric Differences in Leukoaraiosis in Patients with Carotid Artery Stenosis: A Systematic Review

PURPOSE

Despite the prevalence of leukoaraiosis in neuroimaging and its link to dementia, stroke, and death, the exact pathogenesis is still unclear. While some have postulated a link between carotid artery disease and leukoaraiosis, the exact relationship between the two common clinical findings is unknown. To determine the link between carotid disease and leukoaraiosis, we performed a systematic review of interhemispheric differences in white matter disease in patients with carotid artery disease.

METHODS

We performed a comprehensive literature search in multiple electronic databases evaluating the association of carotid artery and white matter disease using both subjective and volumetric assessment of white matter burden. The included studies examined patients with at least 30 % carotid artery stenosis for white matter burden both ipsilateral and contralateral to the site of carotid artery disease.

RESULTS

Of the 2920 manuscripts screened, five were included in the systematic review. One study used a volumetric analysis of the white matter burden and the others used various subjective methods. Four studies found no statistically significant relationship between carotid artery disease and ipsilateral white matter burden and one study found a significantly higher amount of white matter disease ipsilateral to carotid artery stenosis.

CONCLUSIONS

The mixed results in degree of hemispheric leukoaraiosis in patients with carotid artery disease indicate that no definite relationship can be established based on the existing literature. Given the complex nature of carotid artery disease, including increased risk with certain plaque components, the exact relationship requires further investigation with more rigorous research design.

Echolucency of carotid plaques and cerebrovascular events

OBJECTIVES

To assess the relationship between carotid plaque echogenicity and degree of stenosis with acute and chronic stroke.

METHODS

A retrospective study of cerebral MRI and carotid B-mode and Doppler ultrasonography in 60 patients with stroke. Plaque echogenicity was graded as echolucent (1), predominantly echolucent (2), predominantly echogenic (3), or echogenic (4). Sonographic findings were compared between patients with acute (group 1) and chronic (group 2) stroke.

RESULTS

In group 1 (n = 39 patients), the carotid plaques were grade 1 in 21, grade 2 in 22, grade 3 in 9, and grade 4 in 4 carotid arteries. In group 2 (n = 21), the carotid plaques were grade 1 in 2, grade 2 in 8, grade 3 in 4, and grade 4 in 11 carotid arteries. Plaque echogenicity was lower in group 1 than in group 2 (p < 0.05). Plaque echolucency was associated independently with acute stroke from the degree of stenosis.

CONCLUSIONS

Patients with acute infarcts have predominantly echolucent plaques, regardless of the degree of stenosis.

Stratifying risk: asymptomatic carotid disease

Stroke generates significant healthcare expenses and it is also a social and economic burden. The carotid artery atherosclerotic plaque instability is responsible for a third of all embolic strokes. The degree of stenosis has been deliberately used to justify carotid artery interventions in thousands of patients worldwide. However, the annual risk of stroke in asymptomatic carotid artery disease is low. Plaque morphology and its kinetics have gained ground to explain cerebrovascular and retinal embolic events. This review provides the readers with an insightful and critical analysis of the risk stratification of asymptomatic carotid artery disease in order to assist in selecting potential candidates for a carotid intervention.

[Filter content after carotid angioplasty and stenting: relation to ischemic lesions in diffusion-weighted imaging]

OBJECTIVES

To evaluate the relation between the material retrieved from distal filters after carotid angioplasty and stenting and the development of ischemic brain lesions in diffusion-weighted imaging (DWI). To determine the influence of demographic, clinical, and procedural variables in the pathogenesis of emboli and in ischemia after carotid angioplasty and stenting.

MATERIAL AND METHODS

We submitted the contents of the filters of 76 patients (60 men; mean age, 68.39 years; range, 46-82) who had undergone angioplasty and stenting for severe stenosis of the internal carotid artery for histologic analysis evaluating volume (< 1 λ = 0.001 ml = 1 μl; 1-10 λ; and > 10 λ) and the composition of the particles. All patients underwent DWI before and 24 hours after the procedure; we recorded whether lesions appeared and their number, size, and distribution. We correlated the findings with demographic, clinical, and procedural variables.

RESULTS

Symptoms were present before the procedure in 58 (76.3%) patients. Particles were present in 49 (64.5%) of the filters; most particles (77.5%) were 1 λ with a predominance of fibrin-platelet aggregates, cell remnants, and cholesterol crystals. DWI after the procedure detected lesions in 12 (15.8%) patients. We found no statistically significant correlation between filter contents and lesion detection after the procedure or between filter contents and other variables.

CONCLUSIONS

Ischemia after carotid angioplasty and stenting does not depend solely on the embolic load and its nature. We consider that the lower prevalence of postprocedural lesions in our series compared to others suggests that appropriate patient selection and experience minimize the negative influence of some variables like age in their development.

A fully automated method using active contours for the evaluation of the intima-media thickness in carotid US images

The thickness of the intima-media complex (IMC) of the common carotid artery (CCA) wall is important in the evaluation of the risk for the development of atherosclerosis. This paper presents a fully automated algorithm for the segmentation of the IMC. The segmentation of the IMC of the CCA wall is important for the evaluation of the intima media thickness (IMT) on B-mode ultrasound images. The presented algorithm is based on active contours and active contours without edges. It begins with image normalization, followed by speckle removal. The level set formulation of Chan and Vese using random initialization provides a segmentation of the CCA ultrasound (US) images into different distinct regions, one of which corresponds to the carotid wall region above the lumen whilst another corresponds to the carotid wall region below the lumen and includes the IMC. The results of the corresponding segmentation combined with anatomical information provide a very accurate outline of the lumen-intima boundary. This outline serves as an excellent initialization for segmentation of the IMC using parametric active contours. The method lends itself to the development of a fully automated method for the delineation of the IMC. The mean and standard deviation of the thickness of the automatically segmented regions are 0.65 mm +/-0.17 mm and the corresponding values for the ground truth IMT are 0.66 mm +/-0.18 mm. The Wilcoxon rank sum test shows no significant difference.

Comparison of multiresolution features for texture classification of carotid atherosclerosis from B-mode ultrasound

In this paper, a multiresolution approach is suggested for texture classification of atherosclerotic tissue from B-mode ultrasound. Four decomposition schemes, namely, the discrete wavelet transform, the stationary wavelet transform, wavelet packets (WP), and Gabor transform (GT), as well as several basis functions, were investigated in terms of their ability to discriminate between symptomatic and asymptomatic cases. The mean and standard deviation of the detail subimages produced for each decomposition scheme were used as texture features. Feature selection included 1) ranking the features in terms of their divergence values and 2) appropriately thresholding by a nonlinear correlation coefficient. The selected features were subsequently input into two classifiers using support vector machines (SVM) and probabilistic neural networks. WP analysis and the coiflet 1 produced the highest overall classification performance (90% for diastole and 75% for systole) using SVM. This might reflect WP's ability to reveal differences in different frequency bands, and therefore, characterize efficiently the atheromatous tissue. An interesting finding was that the dominant texture features exhibited horizontal directionality, suggesting that texture analysis may be affected by biomechanical factors (plaque strains).

Multidetector row CT of the brain and carotid artery: a correlative analysis

AIM

To evaluate the association between types of carotid plaque, the presence of prior ischaemic events detectable with CT, and patient's symptoms.

MATERIALS AND METHODS

Between January 2004 and May 2006, 112 patients were evaluated using multidetector row computed tomography angiography (MDCTA) of the carotid arteries and computed tomography (CT) of the brain. Carotid arteries were categorized by evaluating the degree of stenosis according to North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria, the type of plaque, and the presence of plaque ulceration. The brain was assessed via CT for the presence, type, and position of lesions. Chi-square tests, Student's t test, and simple logistic regression analysis were performed and the Cohen kappa test was applied for interobserver variability measurement.

RESULTS

The Chi-square test indicated a statistically significant association between the presence of fatty plaques (p=0.005) and CT-detectable lesions in the brain (p=0.004). Moreover, the number of patients with CT-detectable brain lesions was greater in patients with >70% stenosis than in those with <70% stenosis (p=0.007). Logistic regression confirmed the association between fatty plaque and symptoms (p=0.001), between >70% stenosis and symptoms (p=0.041), and an inverse association between calcified plaque and symptoms (p=0.009).

CONCLUSION

MDCTA allows adequate evaluation of the type of plaque. The results of the present study indicate that there is an association between cerebral lesions, symptoms, and fatty plaque in the carotid artery. The degree of stenosis also correlated with cerebral lesions and symptoms. According to the obtained data, the type of carotid plaque should be included among primary parameters in the classification of patients' risk class.

Media thickness measurement of the common carotid artery

The intima-media thickness (IMT) of the common carotid artery (CCA) is widely used as an early indicator of the development of cardiovascular disease (CVD). It was proposed but not thoroughly investigated that the media thickness (MT), its composition and texture may be indicative for identifying the risk of stroke and differentiating between patients with high and low risk. In this study we present an automated method for segmentation of the media layer and measurement of its thickness in ultrasound images of the CCA. The snakes segmentation method was used, and was evaluated on 100 images against manual segmentation. The mean +/- standard deviation (sd) for the manual and the automated IMT measurements were 0.71+/-0.17 mm and 0.67+/-0.12 mm, and for the manual and the automated MT measurements were 0.25+/-0.12 mm and 0.25+/-0.11 mm respectively. There was no significant difference between the manual and the automated measurements. Further research for validating the proposed technique is required and for evaluating it in a larger sample of subjects.

Texture Analysis of Ultrasonic Images of Symptomatic Carotid Plaques can Identify Those Plaques Associated with Ipsilateral Embolic Brain Infarction

OBJECTIVES

The aim of our study was to determine the association between objective, computerised texture analysis of carotid plaque ultrasonic images and embolic CT-brain infarction in patients presenting with hemispheric neurological symptoms.

DESIGN

Cross-sectional study in patients with 50%-99% (ECST) carotid stenosis.

PATIENTS AND METHODS

Carotid plaque ultrasonic images (n=54, 26 with TIAs and 28 with stroke) obtained during carotid ultrasound were normalised and standardised for resolution and subsequently assessed visually for the presence of discrete echogenic or juxtaluminal echolucent components and overall echogenicity (plaque type). Using computer software, 51 histogram/textural features of the plaque outlines were calculated. Factor analysis was subsequently applied to eliminate redundant variables. Small cortical, large cortical and discrete subcortical infarcts on CT-brain scan were considered as being embolic.

RESULTS

Twenty-five cases (46%) had embolic infarcts. On logistic regression, grey-scale median (GSM), a measure of echolucency, spatial grey level dependence matrices (SGLDM) correlation and SGLDM information measure of correlation-1, measures of homogeneity were significant (p<0.05), but not grey level runlength statistics (RUNL) Run Percentage (RP), stenosis severity, type of symptoms or echolucent juxtaluminal components. Using ROC curves methodology, SGLDM information measure of correlation-1 improved the value of GSM in distinguishing embolic from non-embolic CT-brain infarction.

CONCLUSION

Computerised texture analysis of ultrasonic images of symptomatic carotid plaques can identify those that are associated with brain infarction, improving the results achieved by GSM alone. This methodology could be applied to prospective natural history studies of symptomatic patients not operated on or randomised trials of patients undergoing carotid angioplasty and stenting in order to identify high-risk subgroups for cerebral infarction.

Metallothionein expression in the high-risk carotid atherosclerotic plaque

OBJECTIVE

Metallothioneins (MTs) are antioxidant proteins expressed in response to injury. We evaluated MT immunoreactivity in carotid plaques obtained from asymptomatic and symptomatic patients. We also assessed the relationship between ultrasonic plaque echodensity, histological grading, computed tomography findings and MT expression.

METHODS AND RESULTS

In this ongoing prospective study, patients (n = 123, mean age (+/-SD) 68.4 +/- 7.7 years, 97 men) with high-grade carotid stenosis underwent carotid endarterectomy. Specimens were assessed histologically and immunohistochemically. Echolucent plaques (types 1+2) were more common in symptomatic patients (p < 0.0001) and had more advanced histological lesions (p < 0.0001). Echolucent plaques expressed MTs (in macrophages, fibroblasts and T-lymphocytes) significantly more than echogenic plaques (types 3+4) (all p < 0.0001). MT expression was mainly related to carotid plaque echolucency rather than the presence of symptoms. MT expression was significantly more common in advanced histological lesions. Plaques from asymptomatic or symptomatic patients with abnormal computed tomography findings also showed increased MT expression. There was a time-dependent fall in MT expression after cerebrovascular events (p < or = 0.011).

CONCLUSIONS

MT overexpression may be triggered in unstable plaques as a local protective factor. There is a need to identify both causative and protective predictors of the 'vulnerable plaque' in the 'vulnerable patient'. Further studies are needed to resolve these issues.

Snakes based segmentation of the common carotid artery intima media

Ultrasound measurements of the human carotid artery walls are conventionally obtained by manually tracing interfaces between tissue layers. In this study we present a snakes segmentation technique for detecting the intima-media layer of the far wall of the common carotid artery (CCA) in longitudinal ultrasound images, by applying snakes, after normalization, speckle reduction, and normalization and speckle reduction. The proposed technique utilizes an improved snake initialization method, and an improved validation of the segmentation method. We have tested and clinically validated the segmentation technique on 100 longitudinal ultrasound images of the carotid artery based on manual measurements by two vascular experts, and a set of different evaluation criteria based on statistical measures and univariate statistical analysis. The results showed that there was no significant difference between all the snakes segmentation measurements and the manual measurements. For the normalized despeckled images, better snakes segmentation results with an intra-observer error of 0.08, a coefficient of variation of 12.5%, best Bland-Altman plot with smaller differences between experts (0.01, 0.09 for Expert1 and Expert 2, respectively), and a Hausdorff distance of 5.2, were obtained. Therefore, the pre-processing of ultrasound images of the carotid artery with normalization and speckle reduction, followed by the snakes segmentation algorithm can be used successfully in the measurement of IMT complementing the manual measurements. The present results are an expansion of data published earlier as an extended abstract in IFMBE Proceedings (Loizou et al. IEEE Int X Mediterr Conf Medicon Med Biol Eng POS-03 499:1-4, 2004).

Risk factors for periprocedural complications in carotid artery stenting without filter protection

INTRODUCTION

In high-grade stenosis, carotid artery stenting (CAS) may be chosen as an alternative to carotid surgery. Ischemic periprocedural complications may be documented best with diffusion-weighted MRI (DWMRI). In this prospective study serial DW-MRI and color-coded duplex sonography (CCDS) were used to identify carotid stenosis, which is associated with an increased risk of ischemic events due to CAS.

METHODS

High resolution DW-MRI were performed in 74 out of 77 patients before and after CAS. All MRI scans were analyzed in a blinded manner. With CCDS each carotid stenosis was evaluated according to the grade, length, echo properties and plaque surface.

RESULTS

In 42 out of 74 patients (56.8 %) a total of 188 new procedure- related DWI-lesions could be detected, while in 32 patients MRI-controls remained normal. Of the lesions 79.25 % had a size < 1 cm. In one major and two minor strokes due to CAS (total complication rate 3.9 %) corresponding territorial infarcts could be demonstrated. A highly significant correlation was found between the length of the stenosis and the incidence of new DWI-lesions (p = 0.0141). In contrast, neither the grade of ICA stenosis nor the sonographic plaque morphology or plaque surface correlated with the number of DWI-lesion in postinterventional scans.

CONCLUSIONS

The length-and not the degree-of an ICA stenosis seems to be the most decisive sonographic factor for estimating the periprocedural risk of embolism. DWI-lesions are much more frequent than clinical complications and may represent an important surrogate marker for improving the techniques of carotid artery stenting, especially comparing the benefit of different mechanical protection devices.

Management of the Near Total Internal Carotid Artery Occlusion

OBJECTIVES

The risk of stroke in patients with near total internal carotid artery (ICA) occlusion is perceived to be high as stroke risk increases with severity of the stenosis. The management of this entity has not been addressed specifically in the existing randomised trials and thus it remains controversial.

METHODS

Systematic review of the relevant literature.

RESULTS

The management of patients with near total ICA occlusion remains controversial: some favour intervention whereas others have condemned it as dangerous or of no benefit. A prospective multicentre randomised trial regarding intervention versus best medical treatment for patients with symptomatic near total ICA occlusion seems difficult because of the large number of patients required to power the study. Nevertheless, it appears hard to decline surgery based on the current evidence.

CONCLUSIONS

Because of the current controversy over the best management of the near total ICA occlusion, prospective observational studies are needed to demonstrate its prevalence in the symptomatic and asymptomatic population and any associated excess stroke risk. Based on the current evidence, surgery is the treatment of choice in most centres but its validity over best medical treatment remains untested.

Stratified gray-scale median analysis and color mapping of the carotid plaque: correlation with endarterectomy specimen histology of 28 patients

BACKGROUND AND PURPOSE

To determine whether a stratified gray-scale median (GSM) analysis of the carotid plaque combined with color mapping could predict plaque histology better than an overall GSM measurement.

METHODS

Thirty-one carotid plaques derived from 28 patients undergoing carotid endarterectomy were investigated by ultrasound. GSMs of the whole plaque were used as measurement of echogenicity. A profile of the regional GSM as a function of distance from the plaque surface could be generated. Plaque pixels were further mapped into 3 different colors depending on their GSM value.

RESULTS

Plaques with large calcifications presented the highest GSM values, and those with large hemorrhagic areas or with a predominant necrotic core exhibited the lowest. Fibrous plaques had intermediate GSM values. A necrotic core located in a juxtalumenal position was associated with significantly lower GSM values (P=0.009) and with a predominant red color (GSM <50) at the surface (P=0.0019). With respect to the thickness of the fibrous cap and the position of the necrotic core, the sensitivity and specificity of the predominant red color of the whole plaque was respectively 45% and 67% and 53% and 75%; considering the predominant red color of the surface, the sensitivity and specificity increased to 73% and 67% and 84% and 75%, respectively.

CONCLUSIONS

The stratified GSM measurement combined with color mapping showed a good correlation with the different histopathological components and further allowed identification with good accuracy of determinants of plaque instability. This approach should be investigated in a prospective, natural history study.

Association between mitral annular calcification and stroke

It remains controversial as to whether mitral annular calcification (MAC) is an independent predictor of stroke. The aim of this study was to investigate whether there is an association between the presence of MAC and stroke or whether MAC is one of the predictive factors of carotid atheroma and therefore is a secondary risk for stroke. Fifty-six patients who had MAC demonstrated by echocardiography underwent carotid artery duplex sonography and computed brain tomography with various causes were enrolled in the study. They were compared with 58 control patients without MAC. MAC was defined as a dense, localized, highly reflective area larger than 5 mm at the junction of the atrioventricular groove and posterior mitral valve leaflet. Carotid artery stenosis was defined as lumen diameter narrowing exceeding 60%. Cerebral ischemia was detected by spiral tomography and was classified as infarction and lacunae. A significant association was found between the presence of MAC and carotid atheroma (P = 0.011), MAC and hyperechogen plaque (P = 0.034), and MAC and stenosis (P = 0.008). There was an association between the presence of carotid atheroma and cerebral infarction (P = 0.007). Logistic regression analysis revealed hypertension and diabetes mellitus were independent risk factors (P = 0.030, P = 0.034, respectively) for developing carotid atheroma. MAC was an independent factor for carotid stenosis (P = 0.029). MAC may not be a significant causative factor for stroke, but may be a secondary risk factor. A significant association between the presence of MAC and carotid artery atherosclerotic disease may explain the high prevalence of stroke in patients with MAC.

Microembolic signals and carotid plaque morphology: a study of 71 patients with moderate or high grade carotid stenosis

OBJECTIVES

To determine whether particular carotid plaque features on ultrasound are more likely to produce microembolic signals (MES).

PATIENTS AND METHODS

We have reviewed 71 patients with moderate or high grade carotid stenosis established by ultrasound (30-99%). Plaque appearance was classified according to five subtypes. Transcranial monitoring of the middle cerebral arteries was performed on each patient.

RESULTS

MES were more frequently encountered in patients with anechogenic/hypoechogenic plaques compared with isoechogenic/hyperechogenic lesions (P < 0.01). MES+ patients presented also more frequently an irregular surface of the plaque and more severe stenosis, however, the differences did not reach significance. There was no relationship between the presence of MES and a history of stroke or transient ischaemic attack (TIA). When considering the different above mentioned variables (logistic regression), only plaque morphology appeared to be a risk factor for the presence of MES.

CONCLUSION

MES+ patients presented a significantly increased frequency of anechogenic/hypoechogenic plaques. As MES may be a marker of increased risk of stroke, the clinical significance of this particular association should be further investigated.

The impact of the carotid plaque type on restenosis and future cardiovascular events: a 12-year prospective study

OBJECTIVES

to evaluate the impact of the carotid plaque type on recurrent carotid stenosis, future cardiovascular events and patients' survival.

DESIGN

open prospective study.

PATIENTS AND METHODS

three hundred and eight patients who underwent a total of 338 carotid endarterectomies were included in the study. All of the patients were evaluated postoperatively with clinical examination and colour duplex 1 month after the operation and every 6 months thereafter. Mean duration of follow-up was 63 months (range: 12-144). Eight patients (3%) were lost to follow-up. Restenoses, cardiovascular events and deaths were recorded and analysed with regard to the traditional risk factors and the ultrasonographic characteristics of the plaques. Statistical analysis was performed using the Kaplan-Meier method, the log rank test and Cox regression analysis.

RESULTS

cumulative restenosis rate at 10 years of follow-up was 21% and was associated with coronary artery disease (p=0.01) and echolucent plaques (p=0.02). Life-table analysis showed a 10-year survival rate of 64% and a 10-year rate of cardiovascular events of 41%. Hypertension (p=0.003), coronary artery disease (p=0.002) and echolucent plaques (p=0.01) were associated with a higher incidence of cardiovascular events.